1. Field of the Invention
The invention relates to an injection press, and more particularly to an injection press for use in a transfer molding system for fiber reinforced, thermo-setting resins.
2. Prior Art
In injection presses of the specified type, the resin-fiber mixture is deposited in a mold cavity from above by hand, or by means of a semi-automatic loading assembly. The mold is then sealed, and the injection piston moves up and displaces the mixture in the mold cavity. In automatic feeding through a bore hole disposed to the side, the resin-fiber mixture is pressed through an open injection bore hole with a lowered injection piston. The injection piston in such an injection press has free rotation, i.e., only the front part of the injection piston has a diameter such that it has a sliding fit in the injection cylinder. The rear section of the injection piston is produced with a substantially smaller diameter and forms an annular clearance. This is necessary because resin residues lead to the seizing of an injection piston produced with a continuously equal diameter.
A disadvantage discovered with injection presses with freely rotating injection pistons is that a mass of resin can force its way into the annular clearance. Such losses of resin bring about uneven dosage quantities and thereby flaws in the molded article.